Instrument transformers for installation on high voltage transmission lines, which may include those transformers used for protective relay and metering, are large and expensive. This is especially true for instrument transformers designed for applications involving high transmission line voltages. It is also very costly to replace instrument transformers due to the necessity to power down the transmission line during the replacement. One type of instrument transformers are referred to as current transformers (CTs). CTs may be used to measure a flow of current.
Current transformer reclassification is the process of taking an existing current transformer (CT) and recalibrating it, using calibration constants. The calibration constants may be used to modify the current measurements performed by the CT to improve the accuracy of the measured current sensor.
A current transformer reclassification (“sensor”) apparatus may be used to aid in the reclassification of an existing installed CT. In addition, a sensor apparatus may be used to verify end to end system accuracy of CT measurement points in a substation, switchyard, or other location. A sensor apparatus can also be utilized to verify the accuracy and/or operability of new equipment coupled with a transmission line. Currently, meters and instrument transformers are calibrated independently in a lab before being installed as a complete system in the field. However, once installed in the field there is no simple or cost effective way to verify the entire system's accuracy.